1. Field of Invention
The present invention relates to a selective one-way tool.
2. Related Prior Art
A selective one-way tool can be switched between two modes. In the first mode, the selective one-way tool can only drive a fastener in a first direction. In the second mode, the selective one-way tool can only drive the fastener in the second direction opposite to the first direction. Hence, a user does not have to engage the tool with the fastener, drive the fastener with the tool, disengage the tool from the fastener, and repeat this process for many times before tightening or slackening the fastener to a desired extent. The selective one-way tool can be embodied as a screwdriver such as those shown in Taiwanese Patent Publication Nos. 385742, 403020, 578653 and M241178.
Each of theses screwdrivers includes a complicated structure that includes a mode-switching ring, a pawl and a shaft. When rotated in selective one of two directions, the mode-switching ring moves the pawl to selective one of two positions for engagement with the shaft. When a reacting force is too large for the pawl to bear, skid or skip happens so that the user cannot drive the fastener. Moreover, if unintentionally rotating the mode-switching ring in an undesired one of the directions, the user cannot continue to drive the fastener in a desired direction. This sudden loss of the control over the selective one-way tool entails trouble and inconvenience, and might cause danger.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.